Communication of voice information using digital techniques generally involves the use of a voice encoder, sometimes referred to as a voice CODEC or vocoder. The voice encoder samples, digitizes and compresses voice information, e.g., speech, for transmission as a series of frames. Many voice encoders provide variable rate encoding. For example, different types of voice information, such as speech, background noise, and pauses can be encoded at different data rates. Compression enables the voice information to be transmitted at a reduced data rate, e.g., over a wired or wireless transmission channel. Voice information may be digitally transmitted, for example, over packet-based networks, such as networks supporting Voice-Over-IP (VOIP).
Frame-based voice encoding techniques, such as Qualcomm Code Excited Linear Predictive Coding (QCELP), Enhanced Variable Rate Codec (EVRC), and Selectable Mode Vocoder (SMV), encode moments of sound into sequences of bits. The bit sequences represent the sound during the encoded moments, and are commonly referred to as frames. Typically, the encoded frames represent a continuous stream of voice information that is later decoded and synthesized to produce audible output. In particular, the encoded frames may contain parameters that relate to a model of human speech generation. Recognizable speech typically includes pauses following utterances. Accordingly, some of the encoded frames contains the coding of pauses in speech. A decoder uses the parameters received over a transmission channel to resynthesize the speech for audible playback.